PORT ANGELES — Representatives of Nippon Paper Industries USA and the union that represents 130 Nippon workers returned to the bargaining table this week in their second mediation session since a March 20-25 strike.

The Japanese paper manufacturer and Association of Western Pulp & Paper Workers Local 155 have been locked in a 23-month contract dispute that erupted into a strike two days after the company implemented a “best and final offer” that the union had rejected.

Plant workers are being paid and supervised under that contract, which the union has not ratified.

The next is tentatively scheduled for May 7 in a date that is subject to change, Nippon mill Manager Harold Norlund said Wednesday.

The sides also met in mediation April 12.

Greg Palleson, vice president of the international AWPPW, did not return calls for comment on Tuesday’s session.

Norlund said Nippon will not discuss the talks.

“We will not have any comment on mediation or negotiations or ‘cogen,’” Norlund said, referring to the $85 million biomass cogeneration project that is scheduled to go online Sept. 15.

Under the contract the company implemented March 18, some Nippon workers are required to undergo training to run the plant, which will create steam for the mill and which will generate up to 20 megawatts of electricity for which the mill could sell credits to utilities and other buyers.

Nippon manufactures paper for telephone books and catalogs, and newsprint for newspapers including the Peninsula Daily News.

At the same time mediation is occurring, the National Labor Relations Board is reviewing allegations by the union that Nippon engaged in unfair labor practices that mostly occurred during and after the strike.

As of Tuesday, there were 23 allegations of unfair labor practices and more are on the way, AWPPW Organizing Coordinator Paul Cloer said.

If the NLRB finds merit to the allegations, settlement talks will be held between the company and the union.

If a settlement cannot be reached, the NLRB will issue a complaint, which will be heard before an administrative law judge.